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4.17 MLA – Multiply-Accumulate

Syntax:

MLA{<cond>}{S} <Rd >, <Rm>, <Rs>, <Rn>

RTL:

if(cond)

Rd  Rn + (Rs • Rm)

Flags updated if S used:

N, Z (C is unpredictable)

Encoding:

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

cond 0 0 0 0 0 0 1 S Rd Rn Rs 1 0 0 1 Rm

Usage and Examples:

MLA performs a 32x32 multiply operation, then stores the sum of Rn and the 32-bit

multiplication result to Rd. Since only the least significant 32-bits of the multiplication

are used, the result is the same for signed and unsigned numbers.

The instruction below adds the product of R1 and R2 to R0.

MLA R0, R1, R2, R0

4.18 MOV – Move

Syntax:

MOV{<cond>}{S} <Rd>, <shifter_operand>

RTL:

if(cond)

Rd  shifter_operand

if(S==1 and Rd==R15)

CPSR  SPSR

Flags updated if S used and Rd is not R15 (PC):

N, Z, C

Encoding:

31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

cond 0 0 I 1 1 0 1 S SBZ Rd shifter operand

Usage and Examples:

MOV performs a move to a register from another register or an immediate value.

MOV R1, R0, LSL #2 ;R1 <- R0 * 4

MOV R1, #1 ;R1 <- 0x0000001

If the S bit is set and the destination is R15 (the PC), the SPSR is also copied to CPSR.

This form of the instruction used to return from an exception mode.

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ARM ARM7TDMI User Manual Page 26